So-called “tension boards” are commonly used to assist in guiding a workpiece through a table saw, router, shaper, or like woodworking machine, and are well know in the art (see for example, Graham U.S. Pat. No. 2,525,894 and Starnes U.S. Pat. No. 2,699,804). The primary function of such a tool is to maintain lateral force upon a workpiece as it is moved along upright fence structure, albeit the device may also be used to apply downward force for maintaining the workpiece against the table surface.
A commercially available tension board, or featherboard, is described in Morris U.S. Pat. No. 4,476,757. It consists of a body having an array of angularly extending, parallel resilient fingers, and two transverse slots. In use, the body of the featherboard is positioned laterally on an expansion bar, slidably seated in a groove of the machine table, to dispose the free ends of the fingers a suitable distance away from the rip fence (i.e., slightly less than the width of the stock to be cut). The stock is advanced between the rip fence and the ends of the fingers, the resilient deflection of which urges the stock against the fence and holds it firmly while it is being cut by the saw blade.
Despite widespread use, tension boards presently available are believed to be less than optimal in a number of respects. In particular, no presently known device permits movement of the stock in both directions, or at least not readily so. For example, while the structure of the Morris featherboard does provide anti-kickback protection, the same features inhibit rearward withdrawal of the stock. Moreover, the featherboard is not very tolerant of misalignment, it tends to mar the contacted edge of the workpiece (particularly if it is lifted from the table surface), it does not accommodate tapered workpieces, and it does not produce a uniform level of tension along its length or enable significant variation of the level of tension applied to the workpiece.